1. Field of the Invention
The present disclosure relates primarily to video processing, video representation, and video source identification, more specifically, to generation of digital video signature as a compact representation of the video content.
2. Discussion of the Related Art
Efficient video fingerprinting methods to detect duplicate video content for a variety of purposes, such as the detection of copyright infringement, have been explored. It remains a major challenge, however, to reliably detect copyright infringement or other reproductions when the video content has been changed due to formatting modifications (e.g. conversion to another format using a different video compression), scaling, or cropping of the video content either in time or spatially.
As is known to those skilled in the art, video refers to streamed or downloaded video, user generated or premium video in any format, any length or any encoding. A duplicate copy of a video has the same perceptual content as the source videos regardless of video size, format, or encoding. In a near-duplicate or similar copy of a video, some but not all of the content of the video is altered either by changing the duration of the video, by inserting or deleting video frames, or by modifying the size, format, or encoding of the original video.
Recent advances in broadband network speed, video recording and editing software tools, as well as an increasing number of video distribution and viewing sites on the Internet have made it easy to duplicate and edit a video for posting in a video distribution site on the Internet. This leads to large numbers of duplicate and near-duplicate videos being illegally distributed on the World Wide Web (Web).
The sources for duplicate videos on the web may be classified into three categories:                Videos created from broadcast video signals—A user records a broadcast video signal into a computer or digital storage device (e.g. Tivo, DVR) and then uploads this new video to video distribution and sharing sites (e.g. YouTube, Metacafe). The broadcast video and the recorded video may differ in quality and format, but their content is the same or similar (duplicated or near-duplicated).        Videos created from electronic medium—User rips/extracts the video from an electronic medium (e.g. DVD) and duplicates it in a different format. The new video may potentially include additional content or other edits to the original content.        Videos created from existing web videos—User downloads a video from a video distribution/sharing site and uploads it to another video distribution/sharing site. The new video may potentially include format edits, additional content, or other edits to the original content.        
Although the original content is wholly or nearly duplicated, in each case a new video file is generated.
The ease with which videos may be duplicated, modified, and redistributed creates a significant potential for copyright infringement. Further, detecting duplicate and near-duplicate videos on the web is a challenge because of the difficulty in comparing duplicate or near-duplicate videos to the original content. Thus, it would be desirable to have a method to protect the original video content by detecting duplicate and near-duplicate videos such that the copyright owners may receive proper credit and revenue for their original works.
Previous efforts to identify duplicate and near-duplicate videos have used either watermarking or fingerprinting techniques or a combination thereof. The main difference between these techniques is in how the resulting identification marker is stored. Watermarking techniques embed the identification markers into the video file (i.e., video content) while fingerprinting techniques store the identification markers separately as a new file. However, such video identification techniques have not been net without incurring various disadvantages.
With video watermarking techniques, a new watermarked video file is created by embedding an identification marker (visual or non-visual) into the original (source) video file. During the detection phase, video is processed to determine whether the identification marker is present. The video watermarking algorithms add extra identification information to the video buffer or compression coefficients. When a watermark is added to a video buffer, the contents of some of the pixels in the video buffer are modified in a way that the modifications are not recognizable by a human eye but are detectable by the proper watermarking reader software. However, the watermarking techniques are not robust to changes in formatting and encoding of the video. In addition, edits or compressions applied to the video to reduce the file size may similarly degrade the watermark. The afore-mentioned modifications on the video are among possible ways of generating duplicate or near-duplicate videos. Therefore, the watermarking-based solution is not suitable for reliable detection of duplicate or near-duplicated videos.
An alternative approach to embedding an identification marker in the video is to generate a separate video fingerprint as meta-data. The main idea behind fingerprinting is to process a video file to generate unique features (e.g. length, size, number of frame, compression coefficients, etc.) specific to this video with a significantly small amount of data. A duplicate or near-duplicate video is then detected by comparing the resulting fingerprints of two videos for a sufficient number of fingerprints that match. The accuracy and robustness of fingerprinting-based duplicate or near-duplicate video detection techniques are limited by the number of video fingerprints computed, the discriminative power, and the number of fingerprints selected for video comparison. Accurate detection in a large video collection (e.g., billions of video files uploaded to the top ten video distribution/sharing sites) generally comes at the cost of time and computational complexity.